A flexible polyurethane foam (hereinafter also referred to as a flexible foam) is, in substance, produced by reacting a polyol with a polyisocyanate compound in the presence of a urethane-foaming catalyst and a blowing agent. Specifically, a polyol system solution containing a polyol, a blowing agent, a catalyst and the like, and a polyisocyanate compound are prepared separately and mixed, followed by reaction to produce a flexible polyurethane foam.
A flexible polyurethane foam is used, for example, as a material of a seat (a seat cushion or a seat back rest). As an example for a seat cushion, a seat cushion for an automobile may be mentioned.
Particularly, a seat cushion for an automobile is likely to be deteriorated due to external force by the movement of the user during its use, and accordingly improvement in mechanical properties such as the tear strength, the tensile strength and the elongation are desired.
In general, a polyether polyol used as a material of a polyurethane is produced by subjecting an alkylene oxide such as propylene oxide to ring-opening addition polymerization to an initiator such as a polyhydric alcohol by using an alkali catalyst such as sodium hydroxide or potassium hydroxide. In this production process, a monool having an unsaturated bond will form as a by-product. If a flexible polyurethane foam is produced by using such a polyol containing the monool and having a high degree of unsaturation, physical properties of the foam are likely to be deteriorated.
Whereas, the following Patent Documents 1 and 2 disclose a process for producing a flexible polyurethane foam by using a polyol having a low degree of unsaturation produced by using a double metal cyanide complex catalyst instead of the alkali catalyst.